Haptic technology involves simulating virtual environments to allow user interaction through the user's sense of touch. Haptic interface devices and associated computer hardware and software are used in a variety of systems to provide kinesthetic and/or tactile sensory feedback to a user in addition to conventional visual feedback, thereby affording an enhanced man/machine interface. Haptic systems are used, for example, in manufactured component design, surgical technique training, industrial modeling, robotics, and personal entertainment. An example haptic interface device is a six degree of freedom force reflecting device as described in co-owned U.S. Pat. No. 6,417,638, to Rodomista et al., the description of which is incorporated by reference herein in its entirety.
A haptic rendering process provides a computer-based kinesthetic and/or tactile description of one or more virtual objects in a virtual environment. A user interacts with the virtual environment via a haptic interface device. Analogously, a graphical rendering process provides a graphical description of one or more virtual objects in a virtual environment. Typically, a user interacts with graphical objects via a mouse, joystick, or other controller. Current haptic systems process haptic rendering data separately from graphical rendering data.
The graphical rendering of 3D virtual environments has been enhanced by the advent of 3D graphics application programming interfaces (APIs), as well as 3D graphics (video) cards. A programmer may create or adapt a 3D graphics application for rendering a 3D graphics virtual environment using the specialized libraries and function calls of a 3D graphics API. Thus, the programmer avoids having to write graphics rendering code that is provided in the API library. As a result, the task of programming a 3D graphics application is simplified. Furthermore, graphics standards have developed such that many currently-available 3D graphics applications are compatible with currently-available 3D graphics API's, allowing a user to adapt the 3D graphics application to suit his/her purpose. Examples of such 3D graphics API's include OpenGL, DirectX, and Java 3D.
In addition to 3D graphics API's, 3D graphics cards have also improved the graphical rendering of 3D virtual objects. A 3D graphics card is a specialized type of computer hardware that speeds the graphical rendering process. A 3D graphics card performs a large amount of the computation work necessary to translate 3D information into 2D images for viewing on a screen, thereby saving CPU resources.
While 3D graphics API's and graphics cards have significantly improved the graphical rendering of 3D objects, the haptic rendering of 3D objects in a virtual environment is a comparatively inefficient process. Haptic rendering is largely a separate process from graphical rendering, and currently-available 3D graphics applications are incompatible with haptic systems, since graphics applications are not designed to interpret or provide haptic information about a virtual environment.
Furthermore, haptic rendering processes are generally computation-intensive, requiring high processing speed and a low latency control loop for accurate force feedback rendering. For example, in order to realistically simulate touch-based interaction with a virtual object, a haptic rendering process must typically update force feedback calculations at a rate of about 1000 times per second. This is significantly greater than the update rate needed for realistic dynamic graphics display, which is from about 30 to about 60 times per second in certain systems. For this reason, current haptic systems are usually limited to generating force feedback based on single point interaction with a virtual environment. This is particularly true for haptic systems that are designed to work with widely-available desktop computers and workstations with state-of-the-art processors.
Thus, there is a need for increased efficiency in haptic rendering. Improvement is needed, for example, to facilitate the integration of haptics with currently-available 3D applications, to permit greater haptic processing speeds, and to enable the use of more sophisticated force feedback techniques, thereby increasing the realism of a user's interaction with a virtual environment.